In today's vehicles it is usual for a driver of a motor vehicle with a so-called two-pedal system to use an accelerator pedal to demand a clutch torque for propulsion of said vehicle. When the vehicle is being set in motion, the position of the clutch actuator is regulated automatically on the basis of torque feedback so that the clutch torque substantially becomes that demanded by the driver. It is here assumed that the torque generated by the vehicle's engine substantially corresponds to that which the clutch transmits in the vehicle's power train.
This type of strategy causes uneasiness in vehicles with variable engine load caused by power take-off upstream of the clutch in the power train. This uneasiness is due to the position of the clutch actuator being regulated with a view to the engine torque being moved towards a set-point value. The clutch actuator's position will change in response to an unknown disturbance of the engine. This may cause drivers in certain applications with high requirements for precision driving to feel that the vehicle is not behaving in a desirable way. This is due to the clutch torque transmitted not being the same as the engine torque in applications where the engine is subject to irregular loads. If such loads become too great, e.g. when running a powerful AC unit or using power take-off, the driver may see this as a real problem in cases where precision driving is required.
If the load due to a power take-off increases in a vehicle of the kind indicated above, the engine torque will automatically increase, causing an on-board control system to open the clutch somewhat in order to lower the clutch torque towards the set-point value. This means that the force driving the powered wheels decreases and the vehicle's speed is reduced when moving off. Similar problems arise when the load due to the power take-off decreases while the vehicle is moving off, in that the engine torque automatically decreases and the clutch closes somewhat, which may cause a jerk in the power train.
An example of an application where there are problems is where the vehicle is of the so-called hook loader type and precision driving is desirable. A hook loader does for example make it possible to load a container onto the vehicle, without the container being dragged along a sensitive surface, by the driver using precision driving to back in under said container which is held up by the hook loader. It is desirable that the vehicle behave in a predictable way during such operations.
If the vehicle is a hook loader with a so-called three-pedal system, the driver may use the accelerator pedal to speed up the engine, and the clutch pedal to move the vehicle. This results in very good manoeuvrability. In vehicles with two-pedal systems, the driver is deprived of the possibility of precision movement of the vehicle in a desirable way if the clutch actuator's position is no longer predictable, as in applications with variable loads upon the engine upstream of the clutch.
U.S. Pat. No. 5,056,639 describes a device and a method for controlling an automatic vehicle clutch.
EP 1354751 describes a device for controlling a process of setting in motion a motor vehicle with a transmission.
US 20100324790 describes a method for controlling a power train of a motor vehicle.